Subject: Re: [PATCH v1 1/1] drm/drm_panel: Fix EXPORT of drm_panel_of_backlight() one more time

From: Jani Nikula <[email-masked]>
Date: Wed, 18 Dec 2019 12:30:17 +0200

On Tue, 17 Dec 2019, Sam Ravnborg <[email-masked]> wrote:
> On Tue, Dec 17, 2019 at 08:25:03AM -0800, Randy Dunlap wrote:
>> On 12/17/19 6:07 AM, Andy Shevchenko wrote:
>> > The initial commit followed by the fix didn't take into consideration the case
>> > 
>> > CONFIG_DRM_PANEL=y
>> > CONFIG_BACKLIGHT_CLASS_DEVICE=m
>> > CONFIG_DRM_I915=y
>> > 
>> > where symbol devm_of_find_backlight() is not reachable from DRM subsystem.
>> > Quick fix is to avoid drm_panel_of_backlight() from exporting in such case.
>> > 
>> > Fixes: 907aa265fde6 ("drm/drm_panel: fix EXPORT of drm_panel_of_backlight")
>> > Reported-by: Randy Dunlap <[email-masked]>
>> > Cc: Linus Walleij <[email-masked]>
>> > Cc: Sam Ravnborg <[email-masked]>
>> > Cc: Laurent Pinchart <[email-masked]>
>> > Cc: Thierry Reding <[email-masked]>
>> > Cc: Maarten Lankhorst <[email-masked]>
>> > Cc: Sean Paul <[email-masked]>
>> > Cc: David Airlie <[email-masked]>
>> > Cc: Daniel Vetter <[email-masked]>
>> > Cc: Maxime Ripard <[email-masked]>
>> > Cc: [email-masked]
>> > Signed-off-by: Andy Shevchenko <[email-masked]>
>> 
>> Yes, that fixes the build error.  Thanks.
>> 
>> Acked-by: Randy Dunlap <[email-masked]> # build-tested
>
> Hi Andy - thanks for fixing this. And thanks Randy for verifying the
> fix.
> It passed my build test and is now pushed to drm-misc-next.

As I wrote in [1], this allows a configuration that builds and links,
but is silently broken. You won't get backlight support in drm panel
which would be a reasonable expectation with
CONFIG_BACKLIGHT_CLASS_DEVICE=m.

BR,
Jani.

[1] http://mid.mail-archive.com/[email-masked]

-- 
Jani Nikula, Intel Open Source Graphics Center